Dendritic cells (DCs) are antigen-presenting cells (APCs) present in peripheral blood, skin, lymphatic organs, and thymus, and are widely distributed in lymphatic and non-lymphatic tissues (see Steinman, R. M. Ann. Rev. Immunol. 9:271 (1991); Banchereau, J. B. and R. M. Steinman, Nature 392:245 (1998)). Dendritic cells have a strong antigen-presenting ability and express antigenic peptides on class I and II molecules on the dendritic cell surface, which activate CD4 and CD8 T cells, respectively. Through this activation, DCs induce an in vivo immune response against specific antigens (e.g., antigens of pathogenic microorganisms, tumor-related antigens, and transplantation antigens).
The strong ability of DCs to induce immunity is useful in immunotherapy (DC therapy) against many tumors. The present inventors have previously demonstrated that DCs stimulated with Sendai virus (SeV) have a strong anti-tumor effect in mice (S. Shibata et al., J. Immunol, 177: 3564-3576 (2006); Yoneyama, Y. et al., Biochem. Biophys. Res. Commun., 355:129-135 (2007)). The anti-tumor effect depends on the number of DCs inoculated. Clinically, the inoculated DC number is also thought to have a large influence on the therapeutic effect. However, there may be many cases where only a limited number of DC precursor cells (DC progenitors) can be collected due to a patient's condition. As a result, the therapeutic effect may become insufficient due to the insufficient number of DCs obtained. Thus, there is a demand for methods that efficiently expand limited DC precursor cells. Furthermore, to achieve an anti-cancer effect, there is a need for an efficient method for preparing DCs with high interleukin 12 (IL-12) productivity (Cancer Immunol Immunother., (2005) 54:721-728) (Japanese Patent Kohyo Publication No. (JP-A) 2008-515439 (unexamined Japanese national phase publication corresponding to a non-Japanese international publication)).
Prior art documents related to the present invention are shown below.